b does an MCMember delete with a NULL callback
and 0 timeout on unload, which is usually fine since the delete completes
successfully.  However, if ib_sa is unloaded immediately afterwards, the
delete will be canceled and ib_sa will try to call the (now already
unloaded) ib_ipoib module back with the cancel completion, which triggers
the oops.

Signed-off-by: Roland Dreier <roland@topspin.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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